1. Field of the Invention
This invention pertains to a device that measures the optical loss at a specific location on a mirror surface or at a specific location on a lens surface. In particular, it pertains to a device for measuring the degradation of optical loss in real-time by the amount of phase shift in coherent light. This loss is the fractional reduction in optical power which occurs upon reflection of light from the mirror surface.
2. Description of the Prior Art
Previously, each optical characteristic of a sample mirror has been measured separately on a different system. Reflectance, absorption, transmission and scatter have each required separate evaluation techniques. These quantities could be combined for the total optical loss of a sample mirror. In particular, total optical loss was measured as a composite of these characteristics and if a total optical loss system was evaluated, there was no way to measure changes in total optical loss caused by strong or damaging illumination of the surface. Thus, whether the individual characteristics were being measured or an overall figure of merit was being determined, the individual characteristics of a sample mirror were not determined as a function of induced damage. Measurements simply identified before and after characteristics.